dude, i'm not even an fscking gamer, and it's pretty obvious to me that Valve coming to 'desktop linux' is a pretty big deal / good thing. Gaming is huge in Windows land, and both a huge market and technology driver.... You would have to be an idiot to not see that ~ it is a big boost for the linux desktop and is an area where (historically) people have been held back from moving to the platform. (often dual-boot just for gaming, or sticking with Windows) ~ So for 'desktop linux' specifically (ie: not 'linux' specifically) i don't think it is necessarily advocacy to point out that out, since it's just reality.
Honestly, if you have a problem with Valve, then don't buy their products. other than that, I don't see what you think you are going to achieve here, as your arguments just don't pan out.